Simply cover the intakes with aluminum foil, make sure the engine was run for about 3-4 minutes, then you're ready. As mentioned before, the key is using DI water, a safe biodegradable cleaner like P21S Total Auto Wash, a few brushes, and patience. Don't rush anything, and you'll be fine. Once you spray the cleaner on the engine and under the engine door, allow the product to sit for about 5 minutes. Then agitate with a brush, then rinse. Ideally, you would blow the water out of everything using a forced air blower like an Airmax. If you don't have an Airmax, simply dry as well as you can with a microfiber towel, then run the engine for about 5-10 minutes. Dry whatever wasn't dried and paint surfaces with the microfiber towel and a detail spray like einszett Spray Wax, and you're all set. If you want, you can condition the rubber trim around the door with Zymol Tyre or Vinyl. Tyre is also great on your tires and any rubber molding like the ones around the windows. Hope this helps you.

 

You need to cover various parts prior to using any cleaning products, sprays or water.
These include;
•Alternator
•Alarm Housing
•Intercooler
•Battery terminals (if not covered already)
•Induction kit cone (if you have one)
•Coil packs
•Intake opening (Ziplock bag)
Tin foil is a better alternative to using cling-film for the alternator, alarm housing etc as it is easier to mold and has greater protection properties. I suggest you use a plastic bag for the induction kit and just wrap it tight over the end to stop any water ingress. Note: See the warning about this plastic bag further on*
For the intercooler the best way to cover is to get a flat sheet of cardboard and just cut it to size so it fits and covers the fins. Cardboard will normally protect the fins for the duration of the washing. It will get soaked so discard after the wash.